[unreadable] Craving is an important aspect of both the maintenance and relapse to tobacco smoking. The primary purpose of the proposed study is to test the feasibility of and provide evidence for the application of very weak transcranial direct current stimulation (tDCS) (Nitsche & Paulus, 2000) to suppress tobacco craving. We propose using two complementary, cutting-edge neuro-technologies to (1) noninvasively manipulate prefrontal brain activity associated with craving using tDCS (2 mA for 20 min), and (2) measure optically (near-infrared spectroscopy, NIRS) regional cortical hemodynamics in right (R) and left (L) anterior brain regions, which neuroimaging studies have found to be activated during tobacco cue-elicited craving. Adult men and women who are chronic cigarette smokers not seeking treatment will participate. A pre-study mNIRS recording session will acclimate them to the laboratory and assess the reliability and validity of NIRS in this application. They will then be assigned (equated on smoking history and on the genetic addiction susceptibility markers DRD2 and dopamine transporter SLC6A3) into five groups (N=20 each) that receive prefrontal tDCS: anodal R; anodal L; cathodal L; anodal L-not smoking deprived; and sham tDCS (no current). The participants will have been abstinent from nicotine (verified by breath carbon monoxide) except for the L anodal tDCS-not-deprived group. The Tobacco Craving Questionnaire (Singleton et al., 2003, modified from Tiffany & Drobes, 1991) will be administered periodically, and NIRS at four brain sites (R and L dorsolateral and R and L orbitofrontal prefrontal cortices) and psychophysiological measures will be recorded continuously in both sessions (1 week apart). On the study day, all participants (N=100) will have a resting baseline followed by modified cognitive tobacco imagery scripts (Maude-Griffin & Tiffany, 1996). Then, after real or sham tDCS, all participants will be exposed to a virtual-reality simulation of smoking cues. At the end, they will smoke a placebo cigarette (10 mg tar, 0.05 mg nicotine). Directional a priori hypotheses will be tested using multivariate analysis of variance (for repeated measures) and t-tests, as well as rank-order correlations between NIRS R and L brain activation measures and nicotine craving. The proposed study is needed to guide future research on tDCS neurotechnology to supplement conventional smoking cessation treatments and, particularly, to help prevent relapse. [unreadable] [unreadable] [unreadable] [unreadable]